Polymeric materials such as silicone rubber, polyurethane, and other polymers are used as insulation materials for medical electrical leads. For cardiac rhythm management systems, such leads are typically extended intravascularly to an implantation location within or on a patient's heart, and thereafter coupled to a pulse generator or other implantable device for sensing cardiac electrical activity, delivering therapeutic stimuli, and the like. The leads are desirably highly flexible to accommodate natural patient movement, yet also constructed to have minimized profiles.
During and after implantation, the leads and lead body materials are exposed to various external conditions imposed, for example, by the human muscular, skeletal and cardiovascular systems, body fluids, the pulse generator, other leads, and surgical instruments used during implantation and explanation procedures. Accordingly, there are ongoing efforts to identify lead body materials that are able to withstand a variety of conditions over a prolonged period of time while maintaining desirable flexibility characteristics and a minimized profile.